What does a roof inspector actually look at?

The joins, because that is where roofs leak

Water gets in where the roof meets something else: a chimney, a wall, a skylight, a vent pipe, or another roof plane in a valley. Those junctions are handled by flashing, and flashing is the part most often reused on a roof that was otherwise replaced properly. It is the single most common cause of a leak on a roof that looks new.

Valleys carry more water than anywhere else on the roof, so a valley that was shingled over rather than lined is a question of when, not if. Vent boots perish years before the shingles do.

The condition of the field

Then the shingles themselves: curling, cupping, lifting, and granule loss. Granules collecting in the gutters is one of the clearest signals of where an asphalt roof is in its life, which is why the gutters get looked at as part of the roof rather than as an afterthought.

Storm damage shows up here too — lifted or missing shingles, and impact marks that are worth photographing quickly if a claim is possible.

Underneath, and the air

From inside, the decking tells you what the outside cannot. Staining, soft spots or daylight mean water has already been getting past. Bathroom and kitchen fans venting into the attic instead of out through the roof are extremely common on mid-century houses and rot decking quietly from below.

Ventilation gets assessed because poor ventilation shortens a roof more reliably than weather does. Ridge ventilation sized to the actual roof does more for lifespan than paying up a shingle grade.

And what it should produce

Photographs of all of it, including the parts that are fine, so you are looking at the whole picture rather than only the alarming bits. Then a walk-through before any price is mentioned.

If someone inspects your roof and hands you a number without showing you what it is based on, ask to see the photographs. If there are none, there was no inspection.